Compact actuation is required for many devices including, for example, automobiles and other motor vehicles. In addition to being compact, the actuators need to be reliable for a long service life as they are typically mounted in locations that do not have easy direct service access. In addition to space limitations, hysteresis in the drive system may be a limiting consideration. For a gear-driven system, removing play is costly.
Further, some systems require quick response. A particularly difficult application is the damping and control of a vehicle door. A large force must be absorbed in a very short distance and smaller forces must be maintained for extended duration. Play is unacceptable, even with a long moment arm at the door. In addition, the actuator must fit in premium real estate in either the door or the pillar, retaining direct mechanical access to the other element. Still further, the electronic control must have the ability to absorb substantial energy at the ends of door movement when the door is closed and latched and the door is fully open.
This document relates to an actuator or bi-directional element drive system made from an inexpensive electric motor that delivers excellent rotary or linear control without a traditional transmission of any type. The system also has low or essentially no hysteresis. Advantageously, only a small motor is necessary for high force applications. Further in the off state, the system can be designed to be overcome by human effort thereby allowing the opening and closing of the door even in the event of a power failure in the vehicle.